1. Field of the Invention
This invention relates to a method of adjusting a tracer head for use in a profiling machine, and more particularly to a tracer head adjustment method which adjusts the tip position of a stylus of a tracer head to a reference position and makes a zero adjustment of a displacement detector.
2. Description of the Prior Art
A profiling machine performs work while detecting the shape of a model with a tracer head. Since it is desirable that a stylus of the tracer head for contact with the model has a tip configuration conforming to the shape of the machine tool used, an exchange of the machine tool is usually accompanied by an exchange of the stylus with a new one. Such a stylus exchange causes a deviation of the zero point of the displacement detector of the tracer head and a shift of the stylus tip from its reference position due to a difference in weight between the two styli; therefore, readjustment is needed.
The adjustment of the tracer head in the prior art is achieved by adjusting a mechanism in the tracer head. For example, as shown in FIGS. 1A to 1C, a stylus 1 is linked via a displacement transmission mechanism 2 to a core 4 of a differential transformer and the displacement transmission mechanism 2 is suspended by a spring 3 from a support part 6 in the tracer head to establish equilibrium with gravity; in this equilibrium state, the output V from a coil 5 of the differential transformer is zero. In the equilibrium state such as shown in FIG. 1A, if the weight of the stylus 1 increases by .DELTA.W to W+.DELTA.W as a result of its exchange with a new one, the stylus 1 diplaced by .delta. corresponding to .DELTA.W, as shown in FIG. 1B, so that the output V from the coil 5 of the differential transformer becomes V(.delta.) corresponding to the displacement .delta..
In such a state as shown in FIG. 1B, the tip of the stylus 1 shifts from its reference position by .delta. and the displacement detection voltage changes to V(.delta.); and if profile control is conducted without regard to the shifted tip position of the stylus, a large error resulted. Therefore, zero adjustment is needed in which the support 6 is moved by .delta.' so that the tip of the stylus 1 assumes its reference position to reduce the displacement detection voltage to zero, and thereby obtain the equilibrium state.
However, recent miniaturization of the tracer head imposes limitations on the space for the spring 3 for suspending the displacement transmission mechanism 2 and, in addition, entails difficulty on the adjustment of the supporting position of the spring 3. Especially, in a horizontal tracer head, it is difficult to adjustably provide the spring for suspending the displacement transmission mechanism 2 to achieve equilibrium with gravity.